Drainage Design Manual, Hydrology - Flood Control District of ...

Drainage Design Manual for Maricopa County
Hydrology: Indirect Methods
Those procedures are:
1. A graph of seven unit peak discharge versus drainage area curves,
2. Graphs of estimated 100-year discharges versus drainage area for gaged watersheds
in Arizona, and
3. Regression equations and data graphs for flood regions in Maricopa County.
In general, all three procedures should be used when verifying the results of analytic methods.
8.2 INDIRECT METHOD NO. 1 - UNIT PEAK DISCHARGE CURVES
Figure 8.1 presents 7 unit peak discharge relations and envelope curves. A brief description of
each of those curves follows:
A. An envelope curve, based on a compilation of unusual flood discharges in the United
States and abroad (data prior to 1941), by Craeger and others (1945).
B. An envelope curve of extreme floods in Arizona and the Rocky Mountain region
developed by Matthai and published by Roeske (1978).
C. An envelope curve of peak streamflow data developed for Arizona by Malvick (1980).
D. An envelope curve of peak streamflow data for the Little Colorado River basin in
Northern Arizona developed by Crippen (1982).
E. An envelope curve of peak streamflow data for Central and Southern Arizona developed
by Crippen (1982).
F. An envelope curve of the largest floods in the semi-arid Western United States developed
by Costa (1987).
G. An envelope curve of peak discharges for Arizona, Nevada and New Mexico developed
by the U.S. Army Corps of Engineers (1988).
When using Figure 8.1, it must be noted that the curves represent envelopes of maximum
observed flood discharges for different hydrologic regions.
8-2 August 15, 2013